The present invention relates generally to a power take-off arrangement for two-wheel drive motor vehicles equipped with automatic transmissions and, more particularly, to an improved power take-off adaptor constructed for retro-fit installation into standard production drivelines.
A power take-off utilizes the powertrain of a motor vehicle to drive auxiliary mechanisms (winches, hydraulic lifts, etc.) that are either mounted on or carried by the vehicle. While most power take-off arrangements are typically associated with four-wheel drive vehicles having manual transmissions, it is also desirable to provide power take-off capabilities on two-wheel drive vehicles equipped with automatic transmissions.
Modernly, there are three types of power take-off arrangements used in association with vehicles equipped with automatic transmissions. First, a belt-driven power take-off apparatus (PTO) can be mounted to the fan belt section of the vehicle's engine. Unfortunately, due to the large number of auxiliary elements commonly mounted to the engine, and the relatively small space provided within the engine compartment, attachment of a power take-off to the fan belt section of the motor vehicle is rather difficult. Alternatively, some power take-off arrangements utilize a gear fixed for rotation with the output shaft of the automatic transmission for transferring power to a power take-off unit mounted to the transmission casing. While taking power from such a take-off gear in an automatic transmission is advantageous over belt driven systems, the low production volumes typically necessitate expensive rework or modification of pre-existing automatic transmissions. Finally, it is known to couple an "adaptor" between the output shaft of the automatic transmission and the drive shaft of the motor vehicle.
One example of a conventional adaptor is shown in U.S. Pat. No. 4,813,290. Unfortunately, several designs constraints are generally associated with such adaptors which severely impact their utilization in conjunction with high-volume original equipment drivetrain components. More specifically, the automatic transmission housing must typically be reworked to accept "bolt-up" mounting of the adaptor thereto. In addition, the length of the drive shaft must be shortened to accommodate the adaptor housing. Moreover, such power take-off adaptors typically operate to only transmit drive torque from the output shaft of the automatic transmission to either of the power take-off or the vehicle drive shaft. As such, drive torque can only be transmitted to the power take-off when the motor vehicle is motionless. This is undesirable since certain power take-off applications require vehicle movement, such as snowplowing and winching. Furthermore, most conventional power take-off adaptors have no provisions for a speedometer gear or tone wheel such that mileage is accumulated while the power take-off is operated with the vehicle in a stationary condition.